Please, take a look at version 6. In that version you can run mass actions based on the date modifed and assign these users to to a special list, set a field value, send them a mail and much more. You even can automate the whole thing.
Bothe versions use their own set of database tables, so you can safely install them side by side on the same server. That way you can continue to use v5 and get familiar with v6. You can do the final migration any time you want.